An inverted type current transformer has its active part disposed in a metal enclosure disposed at the top of a column insulator. The magnetic core of the current transformer is of metal and toroidal in shape. It is attached to the metal base of the insulator through the intermediary of a hollow metal mast disposed within the column insulator. It carries the secondary winding or windings, the ends of which are brought out through the inside of the mask to bushes disposed on the base of the column insulator.
The primary of the current transformer is formed by a small number of turns wound around the magnetic core at a sufficient insulation distance. It is attached by its ends to the metal enclosure which is at the potential of one end. The metal enclosure and the column insulator are filled with a dielectric material, which may be a gas, for example, which insulates the primary of the current transformer which is at a high voltage from the secondaries and the core, within the enclosure. The column insulator maintains the metal enclosure, which is at the high voltage of the current transformer primary, at a sufficient distance from the ground to ensure its insulation by the air.
The mass of the magnetic core and the height of the column insulator as well as the insulation distances are proportional to the working voltage. Inverted type current transformers for working voltages of the order of 300 kV and above are of a height which exceeds the limits imposed for road and rail transport, and have a magnetic core weighing several hundred kilograms attached to the top of a metal mast several meters high. During transportation on the side, the mass of the magnetic core loads the end of the mast cantilever fashion and may, as a result of impact, impose on the mast considerable bending loads resulting in irreversible deformation modifying the position of the magnetic core within the metal enclosure to the detriment of the insulation distances.
It is known to combat this disadvantage by placing an insulating cone so as to fasten together the top of the column insulator and the top of the mast. This is prejudicial to the quality of the insulation within the metal enclosure and does not completely eliminate the cantilever loading produced by the magnetic core during transport of the current transformer on its side.
The object of the present invention is to remedy these disadvantages.